Molecular Dynamics Simulations of Gas Solubilites Using NMR Chemical Shifts Based Potential Models

We have used the method of molecular dynamics(MD) to examine the solubility of a range of small non-polar gases in a range of solvents, both polar and non-polar. The gases examined include Xe, Ar, CH4, N2, O2, while the solvents include water, n- and cyclo-alkanes, ethylene oxide and mono-ethanol amine. Molecular simulations are an especially valuable tool for predicting solubilities of oxygen in flammable solvents under extreme conditions when experimental studies cannot be carried out safely. When intermolecular potential models were unavailable, we examined the average Xe chemical shifts over a range of temperatures to develop suitable potential models for the cross interactions between Xe and the solvents. The calculation of chemical shifts in MD is an order of magnitude more efficient than solubilities, which makes it an attractive tool for fine tuning potential models. These parameters were then found to be quite transferable to other small non-polar gases. Our results clearly demonstrate that potential models that show better agreement with experiments for chemical shift, invariably lead to better agreement with experiment for Henry's constant and solubility of gases in solvents.